Filters are commonly used in various electronic applications to filter out certain components of an electric signal. Prior Art FIG. 1 shows one example of a commonly known filter referred to as an LC filter. An LC filter basically includes an inductor element L and a capacitive element C combined in parallel.
During use, the LC filter substantially removes, i.e. filters, components of an input electric signal that reside out of a predetermined range, or in other words, are excessively distanced from a desired predetermined frequency, or center frequency f.sub.c. This center frequency f.sub.c is shown in the graph of Prior Art FIG. 2. As shown in the graph, the LC filter suppresses an amplitude, or magnitude, of components of the electrical signal that are either to the right or left of the center frequency f.sub.c. Given this feature, the center frequency f.sub.c of the LC filter may be changed by altering either the inductor element L or the capacitive element C, thereby letting only selected components of the electrical signal to pass.
Yet another aspect of LC filters that serves as a measure of how well an LC filters accomplishes its intended function is the quality factor Q of the LC filter. An LC filter that has a high quality factor Q tends to only pass components of an electrical signal that are very close to the center frequency f.sub.c. With reference to Prior Art FIG. 2, a thinner curve which tightly encompasses the center frequency f.sub.c is indicative of a high quality factor Q. When designing an LC filter, the quality factor Q may be varied by introducing a parallel coupled resistive element R, as shown in Prior Art FIG. 1.
The foregoing LC filter is often referred to as a "bandpass" filter. It should be noted that other types of filters exist which operate under similar principles. For example, "lowpass" and "highpass" filters operate to pass only components of an electrical signal that are less than or greater than a cutoff frequency, respectively.
It thus becomes apparent that two very important features associated with all types of filters may each be controlled by manipulating the various elements of the filter. Prior art methods of manipulating such filter elements, however, are very primitive in that manipulation tends to be done manually. Further, the control of the center frequency f.sub.c and quality factor Q is usually carried out independently.
There is thus a need for an enhanced filter that allows the tuning of a frequency and further the calibration of a quality factor of the filter in an effective manner that may be carried out while the filter is in use.